Cardiac Muscle and Ischemia Quiz

Questions and Answers

What is the most common injury sustained by cardiac muscle?

Injury from excessive workload

Injury caused by infections

Injury due to ischemia (correct)

Injury due to direct trauma

Which characteristic of adult mammalian cardiac muscle limits its ability to regenerate?

Presence of abundant satellite cells

Lack of muscle satellite cells (correct)

Rapid cell division

High levels of growth factors

What happens to the shape of smooth muscle cells when they contract?

They become elongated and thinner

They split into multiple smaller cells

The borders become scalloped and the nucleus distorts (correct)

They maintain a uniform diameter

What connects smooth muscle cells to facilitate communication?

Gap junctions Signup and view all the answers

Which of the following features is unique to cardiac muscle cells?

Intercalated discs Signup and view all the answers

In cardiac muscle, what structure is involved in connecting adjacent cells?

Intercalated discs Signup and view all the answers

What is one reason why the cardiac muscle has a limited ability to repair itself after an injury?

Inability to divide and form new cells Signup and view all the answers

What organelle is concentrated near the nucleus in cardiac muscle cells?

Mitochondria Signup and view all the answers

Which connective tissue layer surrounds individual muscle fibers?

Endomysium Signup and view all the answers

What is the role of the epimysium in muscle tissue?

It surrounds the entire muscle Signup and view all the answers

Which collagen types are found in the connective tissue layers of muscle?

Types I and III Signup and view all the answers

What do the dense collagen fibers in tendons connect to?

Periosteum of bones Signup and view all the answers

What does the myotendinous junction accomplish?

It joins muscle to bone Signup and view all the answers

Which layer of connective tissue surrounds a group of muscle fibers?

Perimysium Signup and view all the answers

Which structure is specifically stained by laminin in muscle tissue?

External laminae Signup and view all the answers

In which section of the muscle can reticulin fibers be found?

In all three connective tissue layers Signup and view all the answers

What does the H zone in the A band indicate?

A region with only rod-like portions of the myosin molecule Signup and view all the answers

Which protein is found on the M line?

Myomesin Signup and view all the answers

What role does creatine kinase serve in muscle contraction?

It catalyzes the transfer of phosphate groups to ADP from phosphocreatine Signup and view all the answers

Which structures alternate to create the striated appearance of skeletal muscle?

Thick and thin filaments Signup and view all the answers

What structural feature bisects the H zone?

The M line Signup and view all the answers

What percentage of total protein in striated muscle do myosin and actin represent together?

Approximately 50% Signup and view all the answers

Where are muscle nuclei typically located in relation to the sarcolemma?

Against the sarcolemma Signup and view all the answers

In a cross section of muscle fibers, what pattern do the myofibrils create?

Hexagonal patterns Signup and view all the answers

What is the primary function of T-tubules in muscle contraction?

To conduct the muscle action potential into the muscle fiber Signup and view all the answers

Which components make up a triad in skeletal muscle?

T-tubules and terminal cisternae of sarcoplasmic reticulum Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

It breaks down acetylcholine to prevent prolonged stimulation Signup and view all the answers

What initiates the contraction cycle in skeletal muscle?

The depolarization of the sarcolemma Signup and view all the answers

What is the primary function of ANF in relation to kidney cells?

Facilitates sodium and water loss Signup and view all the answers

Which structural features are absent in smooth muscle cells as compared to other muscle types?

T-tubules Signup and view all the answers

In what way does the size and number of motor units influence muscle function?

They control the intensity and precision of muscle contraction Signup and view all the answers

Myasthenia gravis affects muscle function primarily by targeting which aspect of neuromuscular transmission?

Binding of neurotransmitters to receptors Signup and view all the answers

What role do dense bodies play in smooth muscle cells?

Link adjacent muscle cells Signup and view all the answers

Which component helps combine the force generated by smooth muscle fibers for coordinated actions, such as peristalsis?

Endomysium and connective tissue layers Signup and view all the answers

What is the function of motor end plates (MEPs) in muscle fibers?

They transmit signals from motor neurons to muscle fibers Signup and view all the answers

What process follows the binding of calcium ions to troponin during muscle contraction?

The exposure of binding sites on actin filaments Signup and view all the answers

In which specific location are the membrane-bound granules most abundant in cardiac muscle cells?

At the nuclear poles Signup and view all the answers

What is the primary ion that smooth muscle cell channels control for contraction initiation?

Ca2+ Signup and view all the answers

What type of muscle cell structure is most similar between cardiac and skeletal muscle?

Presence of dyads Signup and view all the answers

What primarily allows smooth muscle cells to transmit contractile force between adjacent cells?

Dense bodies and cadherins Signup and view all the answers

Study Notes

Cardiac Muscle Injuries and Regeneration

Cardiac muscle injuries primarily result from ischemia, which leads to tissue damage due to insufficient oxygen supply, typically caused by occluded coronary arteries from heart disease.
Cardiac muscle lacks significant satellite cells, resulting in minimal regenerative potential after injury.

Structure of Smooth Muscle

Cross sections of smooth muscle show a variety of cell diameters, with only the largest profiles containing nuclei.
Smooth muscle cells are interconnected by abundant gap junctions, facilitating communication.
When smooth muscle contracts, cell borders become scalloped, and nuclei become distorted.
Mitochondria are concentrated near the nucleus, essential for energy supply.

Skeletal Muscle Composition

Striated muscle exhibits three connective tissue layers: endomysium (surrounds individual fibers), perimysium (encloses muscle fiber groups), and epimysium (surrounds the entire muscle).
These connective tissues contain collagen types I and III, promoting structural integrity essential for muscle function.

Sarcomere Anatomy

Sarcomeres contain dark-staining A bands and lighter I bands. The H zone is a lighter zone within the A band where only thick myosin filaments are present.
The M line holds thick filaments in place with the help of myomesin, a myosin-binding protein, and creatine kinase for energy transfer during contractions.

Muscle Contraction Mechanism

Muscle action potentials are generated by acetylcholine binding to receptors, causing depolarization of the sarcolemma and propagation along T-tubules.
Calcium ions (Ca2+) are released from the sarcoplasmic reticulum, initiating the contraction cycle.
Muscle fibers consist of varied motor units, where a single motor neuron can innervate multiple fibers, affecting contraction intensity.

Myasthenia Gravis

An autoimmune disorder characterized by circulating antibodies against acetylcholine receptor proteins, resulting in muscle weakness and fatigue.

Smooth Muscle Characteristics

Smooth muscle cells lack T-tubules and possess rudimentary sarcoplasmic reticulum, relying on gap junctions for communication.
Dense bodies in smooth muscle act as attachment sites for contractile proteins, effectively transmitting force both within cells and to adjacent cells.
The organization of actin and myosin in smooth muscle differs from striated muscle, allowing for unique contraction patterns such as peristalsis in the intestine.

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Description

This quiz examines the structure of cardiac muscle and the impact of ischemia on its function. It covers key concepts related to muscle injuries from lack of oxygen as well as the unique characteristics of smooth muscle cells. Test your knowledge on these critical aspects of cardiac health.